This invention relates generally to seat belt safety systems for automobiles and more particularly to seat belt safety systems of the type disclosed in my previous U.S. Pat. No. 3,438,455 and No. 3,729,059. In these earlier patents, a system was disclosed which permitted the vehicle's motor to be started when any of the driver's or passengers' seats were occupied with the seat belt buckles unfastened. However, until the buckles were fastened, the vehicle could not be moved because of a detent which engaged the gearshift lever and permitted it only to be shifted between the park and neutral positions. When the seat belts in all occupied seats were fastened, an electrical circuit was completed which activated a solenoid and withdrew the detent from the locking position, permitting the gearshift lever to be operated normally and the vehicle to be moved in any of its forward gears or in reverse.
While the above-described system obviated many objections which were voiced to the so called "ignition interlock system," by permitting the operator of the vehicle to start the engine before the seat belts were buckled, nevertheless, it was found that inconveniences still remained. For example, the vehicle could not be backed out of the driveway without first buckling the seat belts, nor could parking lot attendants deliver the vehicle to a customer, without first buckling the seat belts.